A U.S. Navy 2010 rendering of plans for modifying the bow of new Virginia-class attack submarines, allowing them to carry two sets of six Tomahawk cruise missiles. The Defense Department might use the same launch tubes for fielding a new conventional ballistic missile aboard future Virginia-class vessels (U.S. Navy image).

WASHINGTON -- The U.S. Defense Department plans to develop a new conventional ballistic missile for fielding on attack submarines, according to major budget decisions announced on Thursday at the Pentagon (see GSN, Dec. 23, 2011).

“The Navy will invest in a design that will allow new Virginia-class submarines to be modified to carry more cruise missiles and develop an undersea conventional prompt strike option,” Defense Secretary Leon Panetta said at a press conference.

Obama administration national security leaders -- like their Bush administration predecessors -- have touted the idea of developing conventional military technologies that could attack urgent targets without having to resort to nuclear-armed ballistic missiles. The capability could be used against terrorist leaders spotted at a safe house or a North Korean ballistic missile being readied for launch, officials have said by way of example.

If the new submarine-based missile plan goes forward, it would be the third such proposed system to receive prompt-strike developmental emphasis. Earlier Pentagon plans for long-range submarine- and ground-based missiles have faced some serious political and technical challenges over the past months and years.

Three main options are now under consideration for pursuing the attack submarine-based capability, Global Security Newswire has learned. Under one possibility, a newly designed intermediate-range ballistic missile could be fielded in two new launch tubes designed initially for carrying Tomahawk missiles aboard the Virginia-class vessels.

A second, more ambitious option would be to install in the attack submarines a so-called “four-pack” missile launcher designed for the Trident D-5 nuclear-armed ballistic missiles on future Ohio-class replacement submarines, also known as SSBN(X). Potentially three of the 32- to 36-inch diameter midrange missiles could fit in each of the four Trident-sized tubes, giving the Virginia-class boats a capability to launch as many as 12 of the conventional ballistic missiles.

This alternative would require a major modification to the attack submarines, namely the addition of a “humpback” midsection behind the sail to accommodate the four-pack launch tubes of significantly greater length than the new Tomahawk canisters, according to defense sources.

A third option -- seen as yet more costly and ambitious -- would be to adopt a design for an even wider Trident-capable launch tube for humpback installation on the attack submarines. This would potentially allow for the medium-range missiles to be larger and have longer range, sources said.

Budget pressures could force the Pentagon to stick with the first option -- assuming that lawmakers are even willing to entertain that possibility, according to Hans Kristensen, who directs the Nuclear Information Project at the Federation of American Scientists.

The relatively small size of these attack submarines, relative to the large Ohio-class “boomer” vessels, could accommodate only a limited-range ballistic missile if the boat’s basic design contours are to remain unchanged, he said.

However, any of these options for fielding a prompt-strike capability aboard submarines is almost certain to spark objections in Congress, which has consistently rejected earlier submarine-based concepts that the Defense Department proposed for conventional ballistic missiles.

Lawmakers have generally supported the idea of non-nuclear “prompt global strike,” Pentagon nomenclature for the ability to attack an enemy anywhere around the world on just one hour’s notice, without resorting to atomic war.

Retired Gen. James Cartwright, who served until last year as vice chairman of the Joint Chiefs of Staff, argued in 2005 that advanced conventional-weapon technologies could allow the nation to "drastically" reduce its nuclear arsenal. One military expert subsequently estimated that conventional munitions were capable of destroying up to 30 percent of targets in the nuclear combat plan (see GSN, May 28, 2008).

However, the U.S. Congress, Russian leaders and many nuclear strategy experts warned that fielding conventional ballistic missiles on nuclear-capable submarines could be a potentially destabilizing way to carry out the strike mission. According to this view, Moscow or Beijing might mistake a ballistic missile launch from a submarine for a nuclear salvo, and set loose a devastating response.

In response, the Defense Department in 2008 shifted its main emphasis in the conventional prompt global strike effort to developing an Air Force ground-based weapon called the Conventional Strike Missile (see GSN, Sept. 3, 2008). The maneuverable weapon system was imagined as a hypersonic dart that would initially boost aboard rockets but transition to flight just inside the atmosphere and glide into its target at Mach 20 speeds (see GSN, June 24, 2011).

Lukewarm Air Force support for development of the strike missile, though, and flight test failures by a developmental front-end system -- the Defense Advanced Research Project Agency’s Hypersonic Technology Vehicle 2 -- have thrown into question whether the Pentagon would continue to invest in the ground-based approach, according to defense insiders (see GSN, Aug. 18, 2011).

“Throughout this 10-year process, the Air Force has never gotten enough money to flesh out their designs,” said one retired service officer, ruing the failure to fully explore simpler weapon technologies that might have resulted in a fielded system by now.

“The Air Force money [for this] is actually DARPA money,” and the research agency’s strong role in the effort resulted in highly ambitious technology objectives that proved challenging to attain, according to the former official, who requested anonymity in discussing a politically charged issue.

Before his military retirement, Cartwright last July indicated that if a prompt global strike system is needed urgently to address an emerging threat, ICBM rockets could launch simple conventional payloads at high speed against virtually any target.

"I mean, we use cement to test with today," Cartwright said. "It makes a very big hole."

Other fairly straightforward options eyed under the Air Force missile effort have involved off-the-shelf munitions installed on the front end of the hypersonic boost-glide missile, according to officials.

Panetta’s effort to reduce the defense budget by $487 billion over the next decade -- mandated by a deficit-reduction law passed last year by Congress -- has affected more than just the Air Force missile, according to defense insiders. The entire conventional prompt global strike initiative will be getting significantly less funding than anticipated, sources said.

In internal Defense Department deliberations, the multiservice prompt global strike effort lost roughly two-thirds of its projected budget for fiscal 2013 through 2017, GSN has learned.

Congress funded the multiservice Pentagon account for prompt global strike at $180 million in fiscal 2012. Of that amount, the Pentagon directed $10 million to the Navy to study the medium-range missile concept, according to defense sources.

An intriguing twist to Thursday’s announcement is that the Pentagon leaders and documents referred to the new submarine-based missile effort as “a conventional prompt strike option,” dropping the word “global.” That more-limited description dovetails with reports that the missile would be designed with intermediate range, generally understood to be about 1,800 to 3,500 miles of flight.

That contrasts with a long-range missile, such as today’s nuclear-armed ICBMs, capable of hitting targets on the other side of the world from bases in the continental United States.

It appears that the midrange missile would continue to use prompt global strike funding, though the fate of the Army-, Air Force- and DARPA-led efforts in the president’s upcoming fiscal 2013 budget remains unclear.

Cheryl Irwin, a Pentagon spokeswoman, would not address directly any implications that funding the submarine missile design effort might have for the seemingly ailing Air Force-DARPA Conventional Strike Missile.

“This budget will focus this development on a submarine-launched option,” she said in written response to a reporter’s questions. “There are other efforts that are ongoing.”

Asked whether fielding the missile aboard submarines might raise the same hackles on Capitol Hill and elsewhere that the earlier Trident-modification effort did, Army Gen. Martin Dempsey said differences in the technology should afford the new approach broader acceptance.

Compared to the prior Trident missile-based concept, “the technology and therefore the trajectory that would be required to deliver it” would be different for the medium-range missile being sought today, the Joint Chiefs of Staff chairman told reporters at the Thursday event. “There's [also] the speed at which these delivery systems can move.”

He added: “You can lower the trajectory and therefore avoid the confusion you're talking about in terms of it being mistaken for an ICBM with a nuclear warhead.” Dempsey also alluded to additional factors that could differentiate this new missile from existing nuclear-armed weapons, but did not identify them.

Kristensen was skeptical that the new missile, if placed aboard a stealthy attack submarine, would ease concerns about potentially destabilizing ambiguity during a crisis.

“Even a conventional intermediate-range ballistic missile launched from a converted Virginia-class attack submarine could be misinterpreted because its compressed trajectory would look much like a nuclear D-5 launched in a compressed trajectory as part of a first strike,” he told GSN. “And it’s still unclear to me why it is so important to have a conventional ballistic missile against terrorists and rogue states, given the overwhelming firepower that we deploy today.”

In a document released on Thursday, titled “Defense Budget Priorities and Choices,” the Pentagon characterized its decision to invest in the submarine-based capability as part of its effort to “rebalance toward the Asia-Pacific and Middle East regions.”

Defense leaders debuted this regional shift in U.S. focus earlier this month as part of new military strategic guidance, based on force draw downs in Iraq and Afghanistan and mandates to reduce Pentagon spending over the next decade (see GSN, Jan. 6).

Offsetting some of the budget reductions proposed over the next fives years totaling $259 billion -- compared to previous spending plans for the same time period -- defense leaders said in the newly released document that they “increased or protected investment in capabilities that preserve the U.S. military’s ability to project power in contested areas and strike quickly from over the horizon.”

Among these focused investments would be to develop a new stealth bomber to replace today’s fleet of nuclear- and conventional-capable long-range aircraft.

The new Asia-Pacific emphasis -- which many defense experts interpret as largely a response to China’s rising role in the region -- “requires an Air Force that is able to penetrate sophisticated enemy defenses and strike over long distances,” Panetta said at the Thursday news briefing. “So we will be funding the next-generation bomber, and we will be sustaining the current bomber fleet.”

No previously unanticipated U.S. nuclear reductions would be included in Obama’s fiscal 2013 budget request, said Ashton Carter, the deputy Defense secretary, in a follow-on press conference.

The White House is “considering the size and shape of the nuclear arsenal in the future,” he said in response to a question about whether further atomic cuts must await new negotiations with Russia following last year’s New START agreement. “When those decisions come, we'll factor them into our budget,” Carter said.

The spending plan does foresee a two-year delay in a Navy effort to replace its Ohio-class ballistic missile submarines, which Carter said would reduce schedule risk in what had previously been an “aggressive” developmental plan, “maybe even verging on optimistic” (see related GSN story, today). Prior expectations had the new submarine first being deployed in the 2029.

Along with these nuclear-capable strike systems, the Pentagon will also “design changes to increase cruise missile capacity of future Virginia-class submarines” and design “a conventional prompt strike option from submarines,” the document states.

If the simplest of the three options for giving the attack submarines a ballistic missile capability is embraced, launch tubes being built for Tomahawk cruise missiles on the stealthy underwater vessels could do double duty as launchers for the new medium-range ballistic missile.

A redesigned bow for new Virginia-class subs would allow for the emplacement of two launch tubes, each of which is expected to accommodate six Tomahawks, according to Defense Department documents. A 2010 Navy briefing on its submarine development and fielding plans depicts the location of the two tubes, each capped by a lid, in front of the submarine sail.

Each launch tube could be fitted with at least one -- maybe more -- of the new medium-range ballistic missiles, permitting a total of two or possibly additional ballistic missiles in each modified submarine, defense sources told GSN.

The Navy is currently buying Virginia-class attack vessels at a rate of two per year. Procurement is in a series of “blocks,” with incremental upgrades expected in each block of submarines, according to a fiscal 2011 Pentagon report on test and evaluation.

Eight Block 3 submarines, beginning with the 11th Virginia-class hull built, will for the first time feature the new, wide-diameter launch tubes. The two wide tubes replace 12 narrow vertical launch tubes for launching the same number of Tomahawks.

The design for next set of boats in the series, Block 4, has not yet been finalized.

Irwin, the Defense Department spokeswoman, would not say on Thursday how much the new-design ballistic missile might cost, how many of the weapons could be procured or how soon they might be fielded.

A “sea-based prompt-strike missile is in the early stages of development” so these details “are not yet available,” she said in the written responses.

With the new design and procurement of U.S. ballistic missiles typically running into hundreds of millions of dollars or more, Kristensen was skeptical that Congress would embrace the Pentagon initiative at a time of budget restraint. The Pentagon could face yet another roughly $500 billion in reductions if lawmakers are unable to negotiate an alternative to the budget “sequester” process by the end of this year.

“Congress is very unlikely to pay for an entirely new ballistic missile,” the longtime defense analyst said.

In fact, the new submarine missile initiative appears to be based on an initial design concept first discussed under the Pentagon’s conventional prompt global strike effort several years ago, he noted (see GSN, March 20, 2008).

For her part, Irwin hinted in response to questions that basing the missile aboard the Virginia-class submarines is not the only option under consideration.

“The development is not service specific,” she said. “The current focus is a submarine variant, but we are very early in the R&D process.”

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